This disclosure relates to a fuel system, and particularly to a system that includes hydromechanical control of the fuel system associated with a positive displacement pump that delivers desired fuel flow from an upstream supply to a downstream engine.
Traditional fuel systems use a metering valve and bypass valve in conjunction with a positive displacement pump to control flow to an engine. This configuration requires a minimum pressure rise across the positive displacement pump to provide control for the bypass valve. If the bypassed fuel was returned to a centrifugal stage further upstream, the minimum pressure rise can be satisfied but there is an increase in the required pump input power.